The invention relates, to an orthodontic dental appliance.
In order to correct dental malformations both on the upper or maxillary arch and on the lower or mandibular arch, it is known to use appliances which, within the framework of orthodontic treatment, make it possible to straighten badly positioned teeth by imparting to them forces tending to straighten them axially, that is to say in a lateral plane or under xe2x80x9ctorquexe2x80x9d, that is to say in the anteroposterior plane.
Current appliances comprise, for each dental arch, housings or supports, also called brackets, which, glued to the inner or outer face of each of the teeth, comprise, as shown in the accompanying FIG. 1, on the one hand, a base b, in which is made a horizontal groove f capable of receiving an arch wire d which is composed of a nonoxidizing metal alloy and to which the base is connected by means of a tie consisting of a ring of synthetic material or a metal wire.
Each housing is specific to a tooth, and the horizontal slots made in the housings have an angulation relative to their base both in the frontal vertical plane and in the anteroposterior vertical plane. These angulations vary as a function of the teeth on which the housings must be arranged and of the intended straightening. Likewise, the arch wires are selected from a series of a plurality of arch wires differing from one another in the morphology of the dental arches and, as regards each dental arch, in the straightening forces which the branches provide. In practice, the metal arch wires have a more or less large round, square or rectangular cross section and are modified as treatment progresses.
In a distalization phase of some teeth, the ends of the arch wire are connected to means which impart to it a tensile force toward the rear, that is to say in the direction of the interior of the mouth, and are generated by external pericranial support means. As treatment progresses, the orthodontist adapts the force generated by the arch wire and those forces generated by possible intermaxillary connections between the maxillary corrective element and the mandibular corrective element, so as to adjust the repositioning of the teeth.
In some appliances, each arch wire is inserted horizontally into the grooves of the housings fastened to the maxillary teeth and to the mandibular teeth. Since each groove issues horizontally, the wire is held insufficiently, this being conducive to the version or axial rotation of the teeth during treatment and consequently slowing down the corrective effects of this treatment.
The same is true of appliances in which, as described in U.S. Pat. No. 5,374,187 and U.S. Pat. No. 4,585,413, the horizontal groove for receiving the arch wire is made in an intermediate bridge connecting the base to an anterior wall and issues vertically in the direction of the occlusal plane or of the gum. This is because, if the connection to the arch wire is not firm, has play or is made punctually, it makes it possible, under the straightening force imparted by the arch wire, for the tooth to tilt by pivoting about the resistant center of the latter, said center being located midway up the root. During treatment, the tooth pivots in one direction and the other, generating, on the root, stresses which may lead to resorption, that is to say to a reduction in its length, and even to the loss of the tooth.
One object of the invention is to overcome these disadvantages by ensuring a positive connection between housing and arch wire, making it possible, by means of a low straightening force, to straighten the tooth in a translational movement, or aggression, without any version of the root.
With current appliances, it is necessary, in the distalization phase, to make use of an extra-oral pericranial support appliance for generating the straightening forces on the arch wires. This solution is demanding for the patient and, above all, because of its pericranial support, sometimes causes headaches which may have an adverse effect on cranial and basicranial structural growth, particularly in young patients at risk who have disorders of the temporomaxillary joint or of vertebral statics.
Another object of the invention is to provide an orthodontic appliance which avoids any need for extra-oral pericranial support tractions.
Another disadvantage of this current type of appliance is its unesthetic nature, disclosed in FIG. 1. Specifically, even if each housing comprises an anterior face composed of ceramic or the like of the color of ivory, the metal arch wire forms a highly visible dark-colored girdle which attracts attention and mars the dental arch.
Likewise, the elastomeric ties connecting the housings to the arch wires gradually add to the unesthetic appearance, since, under the action of the saliva, they swell, lose color and become yellow.
Another object of the invention is to provide an appliance which has little adverse effect on the esthetic appearance of the dental arches.
Finally, because of its uneven shapes, each housing promotes a substantial retention of dental plaque both on its visible and on its nonvisible parts. This dental plaque gives rise to risks of leucomas, coloration, enamel stains and even decay.
Another object of the invention is to reduce the formation of dental plaque where it is formed and to make brushing easier.
The invention relates to an appliance which, for each in each case maxillary and mandibular dental arch, is composed:
of a series of arch wires forming a U-shaped arc, surrounding each dental arch and differing from one another in the straightening forces which their branches supply, said wires having a rectangular cross section, with their small sides parallel to the occlusal plane,
of metal housings which are fastened by their base being glued to a defined tooth and of which those for the incisors, canines and premolars comprise a horizontal groove for receiving the arch wire, said groove issuing in the direction of the occlusal plane and being formed in an intermediate bridge connecting the base to an anterior wall, while the housings for the molars comprise a tunnel for positioning the end of the corresponding branch of the arch wire,
of ties, such as elastic rings, for tying the arch wire in the grooves of the housings,
and of means imparting, at least to the maxillary arch wire and in one treatment phase, a tensile force directed toward the rear.
According to the invention, each of the housings for the incisors, canines and premolars comprises, for attaching an elastic ring for tying to the arch wire and in the intermediate bridge, on one side, between the base and the groove for the arch wire, an anchoring flute issuing in the direction of the occlusal plane and, on the other side, between the base and the anterior wall, a horizontal groove issuing opposite the groove for the arch wire, while the anterior wall has a width and a height greater than those of the base and than those of the intermediate bridge, in order to mask this bridge and the elastic ring for tying the arch wire.
By means of this appliance, the arch wires are inserted from the occlusal part toward the gingival part, thus making the practitioner""s task easier. The arrangement of the grooves for the elastic ring considerably improves the hold of the arch wires which can thus carry out more efficient dental correction, without unwanted movements.
The housings are very easy to clean, as are, moreover, the base and the intermediate bridge, since, where most of the housings are concerned, these parts are free of protuberances and various projections.
In esthetic terms, the anterior walls conceal from view not only the housing, but also part of the arch wire and the ties of the arch wire to the housing, thus doing away with the metallic appearance of current appliances.
When the tie is put in place, it is concealed completely by the anterior wall and therefore cannot, over time, impair the esthetic appearance of the appliance, for example by becoming yellow under the action of saliva.
In one embodiment, the tie formed by the elastic ring comprises two loops surrounding the parts of the arch wire which project longitudinally from the intermediate bridge, and these loops are obtained as a result of the elastic ring being put in place around the intermediate bridge, in the flute and in the groove of the housing, then, after the introduction of the arch wire into the groove, of the elastic ring being pivoted around the arch wire for the purpose of attaching its loop coming from the flute in the opposite groove.
By virtue of the two loops, the arch wire is wedged firmly in the groove in terms of vertical translation, horizontal translation and longitudinal translation, so that the tooth cannot pivot relative to said arch wire and, under the straightening force, can be displaced only in a translational movement parallel to itself, without any effect on its root.
In one embodiment, and for carrying out the straightening of complex pathologies, each housing for the canines and premolars comprises, in its part between the base and its anterior part, a vertical well issuing into the groove for the arch wire and forming, with a flute made in the bottom of said groove, an anchoring member for the bent end of one of the branches of a kickover spring for the axial straightening of the tooth, the other branch of this spring being provided with an end hook hooking onto the arch wire.
Thus, the straightening of a tooth by means of a housing of this type is carried out by the kickover spring which comes to bear with one of its branches on the arch wire and, by its other branch cooperating with the intermediate bridge, imparts the axial straightening force to the housing and therefore to the tooth to which this housing is fastened.
In one embodiment, the appliance comprises a maxillary arch wire for the bilateral distalization of the molars and canines, comprising, on each of its lateral branches, on the one hand, a helical spring which is arranged around said branch and the anterior end of which is connected to this branch by means of a weld arranged on a zone of this branch which is set back from the canine, while the posterior end of this spring comes to bear on the housing of a molar, and, on the other hand, a vertical hook which, projecting upward from a part of the branch which comes between the lateral incisor and the canine, forms an attachment means for one of the ends of an elastic intermaxillary traction ring, the other end of which is attached to a gingival hook projecting from the housing fastened to the first mandibular molar.
This device, used in a first therapeutic stage, makes it possible to dispense with any other means for putting the arch wire under traction and, in particular, with the pericranial support means. Said device is easily inserted between the gums and the cheeks and, by virtue of the good connection between the arch wire and the grooves of the housings subjected to stress, makes it possible to reduce the straightening time.